Oil burner, more particularly for continuous-flow heaters



E. KEPPEL. 3,397,940

MORE PARTICULARLY FOR CONTINUOUS-FLOW HEATERS Aug. 20, 1968 OIL BURNER,

Filed Oct. 18, 1966 IN VEN TOR:

United rates Fatent Q 9 Claims. Cl. 431-28) ABSTRACT OF THE DISCLOSURE A fuel oil gasification burner has a fresh air intake valve comprising a flap mounted on a shaft for rotation thereabout. The shaft is spring loaded to the valve closed position and an electric servomotor connects to the shaft to open the valve when the servomotor is energized. A solenoid valve is connected in the oil line between the oil pump and the burner. A thermostat is positioned to measure the temperature in the burner. The air valve shaft has a cam which actuates two electric switches, one being closed when the air valve is partially open and remaining closed as the air valve moves to the fully opened position. The second electric switch is normally closed and is opened after the air valve moves to the fully open position. An electric ignition device is provided. The electric circuitry is such that when electric power is provided and the burner is cold, a burner heater commences operating. The thermostat turns on the servomotor after the burner temperature has been raised to a given temperature to commence opening the air valve. When the air valve has partially opened the first electric switch closes to open the solenoid fuel valve. When the air valve has fully opened the second switch opens to shut off the electric ignition device.

The present invention relates to an oil burner, more particularly for continuous-flow heaters. For such continuous-flow heaters used to heat hot water for domestic water or also for hot water circulation heating, oil gasification burners with non-luminous blue flame are primarily suited, as they are, for instance, described in greater detail in US. Patent 3,238,991. An oil burner of the type indicated is supplied with the air of combustion via a controllable fresh air flap by a motor-driven blower, and the oil supply is effected by means of an oil pump via a solenoid valve. It is the object of the present invention to improve on the control of an oil burner of the type indicated and to render the same more definite, wherein it is of importance to manage with as few and simple control devices as possible. In prior art oil burners the solenoid valve controlling the oil supply is opened via an electrically heatable bimetallic switch so that the oil supply takes place with delay after starting of the air blower and opening of the fresh air valve. The moment of energization of the solenoid valve with such bimetallic switch is not well defined and is independent of the position of the fresh air valve. If, for some reason or other, the fresh air valve does not open in time or does not open at all, oil can nonetheless be injected into the oil burner, which may, of course, lead to considerable difiiculties, even if the burner is equipped with a flame monitor.

The present invention resides in the fact that, for avoiding these difliculites, the solenoid valve releasing the oil supply is energizable in dependence on the position of the fresh air flap. Provision can be made that the oil supply is eflected in a specific position of the fresh air valve flap, for instance, when the fresh air valve is, say, half opened, which is advantageous in some respects. Namely, the ignition may take place when there is a certain lack of air, the result thereof being that the flame has a better adhesion to the burner opening which is still cold.

Expediently, the invention is realized in that a trigger cam is mouted on the shaft of the fresh air flap which cam actuates a microswitch arranged in the electric circuit of the solenoid valve. The shaft of the fresh air flap may be rotatable by an electric servomotor against a restoring spring. In oil burners wherein prior to starting there is an electric heating of the burner, the servomotor adapted to open the fresh air flap can suitably be switched on by a burner thermostat which also serves to switch off the electric heating. Together with the switching on of the servomotor, the switching on of a burner ignition device can be effected simultaneously by the burner thermostat, it being advantageous if the burner thermostat is adapted and adjusted such that the switching on of the servomotor takes place prior to the switching off of the burner heatmg.

Frequently, in oil burners there is provided a flame monitor which operates in accordance with the flame ionization principle. It has shown that the flame ionization is disturbed when the ignition device is switched on, and consequently, the ignition device must be switched off if flame monitoring by ionization shall become operative. On the other hand, the ignition device, after release of the oil supply, must remain switched on long enough to ensure an ignition of the burner. In further modification of the present invention, with a burner having an ionization flame monitor, provision is therefore made that the burner ignition device can be switched off automatically when the open position of the fresh air flap is reached. Thus, the opening movement of the fresh air flap is effective to switch on the oil supply as well as switch off the burner ignition device at a time interval so that in operating condition an undisturbed flame monitoring can take place. The arrangement is conveniently provided such that the trigger cam mounted on the shaft of the fresh air flap is formed with a lug which, in the open position of the fresh air flap actuates a microswitch arranged in the electric circuit of the burner ignition device.

An embodiment of the present invention is hereinafter more fully explained by reference to the accompanying drawings, wherein FIG. 1 illustrates schematically the design and the circuit of a continuous-flow heater operating with an oil burner, wherein FIG. 1a is an enlarged schematic view showing the fresh air intake and the con-trol elements connected with the fresh air valve.

FIG. 1b and FIG. 10 correspond to FIG. 1a in other operating positions.

FIG. 2 is a side elevation of the fresh air flap control device.

FIG. 3 illustrates schematically the burner thermostat and the switching mechanism thereof.

A continuous-flow heater 1 has incorporated therein an oil gasification burner 2 which is supplied with oil by an oil pump 3 via a magnet valve 4 and an oil-pressure pipe 5 connected to an injection nozzle. At the same time, fresh air sucked in by a motor-driven blower 6 via a fresh air socket 7, is injected into the burner 2. The fresh air socket 7 illustrated on an enlarged scale in FIG. 2 has arranged therein a fresh air flap or valve 8 which is mounted on a shaft 9. The shaft 9 is under the influence of a restoring spring 10 which tends to bring the fresh air flap 8 into closed position. An electric servomotor 11 connected to shaft 9 is counteracting the restoring spring 10, which servomotor when being energized opens the fresh air flap 8 and keeps it open. A cam plate 12 is mounted on the shaft 9 of the fresh air flap 8 which with a trigger cam 12' thereof actuates a microswitch 13 when the fresh air flap 8, as is illustrated in FIG. 1b, is

half open. A lug 14 of the cam plate 12 actuates a second microswitch 15 when the fresh air flap 8 is fully opened.

The oil burner 2 has incorporated therein the heat Sensor 16 of a burner thermostat 16 (FIG. 3) being formed with a switching lever 17. The switching lever 17, when the temperature in the burner 2 increases, is moved from the switching position I via the switching position II into the switching position III. The switching lever 17 c0- operates with two contact faces 18, 19. In the switching position I lever 17 only contacts the contact face 18. In the switching position 11 it contacts both contact faces 18, 19 and in the switching position III it contacts only the contact face 19. The contact face 18 has an electric heater coil 20 connected thereto. Coil 20 is arranged in the burner 2 and serves to heat up the burner 2 prior to starting operation thereof. The contact face 19 has connected thereto a line 21 leading to a distributing point 22, while the switching lever 17 connects to a distributing point 23. A wire connects distributing point 23 to a control unit 24 and wire 31 connects the latter to a main switch 25 leading to voltage source. A wire 32 connects distributing point 23 to the switch 13 and a wire 33 connects the switch to the solenoid valve 4 in series-connection. From the distributing point 22 one connecting line 34 leads to the servomotor 11 and a wire 35 to the switch 15. A wire 36 leads from switch 15 to the control unit 24 in the electric circuit of an ignition transformer 26. The ignition transformer 26 supplies ignition electrodes 27 which are arranged in the burner 2. The control unit 24 has connected thereto a flame monitor 28 based on the flame ionization principle. The motor of the blower 6 can be switched on via the main switch 25.

The operation of the arrangement as hereinbefore described is as follows:

If the oil burner 2 is started in a cold state, the main switch 25 must be closed. Thus, the blower 6 starts with fresh air flap 8 closed. At the same time a voltage is produced at the distributing point 23 so that the heater coil 20 is switched on via the contact lever 17 and the contact face 18 and heats the interior of the burner 2. The heated air in the burner 2 is circulated by the blower 6 without fresh air supply and a uniform temperature is produced. After a sufficient temperature has been reached, the burner thermostat 16 causes the switching lever 17 to assume the switching position H at which the distributing point 22 also has a voltage applied thereto via the contact face 19. The heater coil 20 is not yet switched off. Via the distributing point 22 the servomotor 11 has a voltage applied thereto and starts running by slowly opening the fresh air flap 8. As soon as the fresh air flap has assumed the position as illustrated in FIG. 1b, the cam 12' is effective to actuate switch 13 and thereby the solenoid valve 4 releasing the oil supply is energized. Now, the pump 3 is effective to inject oil into the burner 2, while the fresh air supply is still restricted, and this oil is gasified and evaporated, respectively, and ignited by the ignition electrodes 27. In the meantime, the temperature in the burner 2 has increased so much that the switching lever 17 of the burner thermostat 16 has assumed the switching position HI, whereby the heater coil 20 has been switched off with delay. The ignition remains in operation until the fresh air flap 8 is fully opened (FIG. 10) and the switch 15 has been actuated to the switch open position by the lug 14 of the cam plate 12. Thus, the ignition is in operation long enough to ensure a definite ignition. After the ignition has been switched off, which is effected by the switch 15 in dependence on the full opening of the fresh air flap 8, the burner 2 is in operation and is monitored by the control unit 24 and the ionization flame monitor 28, respectively, in known manner.

To summarize, with the arrangement as hereinbefore described the following advantages accrue:

The oil supply is released by the solenoid valve 4 only when the fresh air flap is opened sufiiciently. Since the blower 6 is switched on prior to the servomotor 11, it is ensured that the blower motor has already reached a full speed prior to the initiation of the oil supply. The burner 2 remains in full operation only when the fresh air flap 8 is fully opened, since in that case only, the ignition is switched off and in that case only, the ionization monitoring can become effective.

The invention is claimed as follows:

1. In a fuel oil gasification burner of the type including a fresh air intake valve, a valve operating device connected to said valve to open and close the valve, a heater to raise the temperature of the burner prior to ignition of the burner, and a fuel oil supply device, the improvement comprising: thermostatic means operatively connected to said burner and including first electric switch means actuated in response to the temperature in the burner; second electric switch means operatively connected to the air intake valve to be actuated by the position of the air intake valve; and circuit means connected to and including said first and second switch means and connected to said heater, said control device and the valve operating device for energizing said heater when the burner is cold, when electricity is supplied, energizing the valve operating device to commence moving the air valve toward the valve open position and to actuate the second switch means to energize the oil supply device to commence supplying oil only after the air valve has at least partially opened.

2. In a burner as set forth in claim 1, wherein said first switch means deenergizes said heater when the temperature in the burner has been raised to a predetermined temperature.

3. In a burner as set forth in claim 2 and including an electric ignition device, wherein said circuit means connects the ignition device to the second switch means to energize the ignition device when the air valve is closed and to deenergize the ignition device when the air valve is open.

4. In a burner as set forth in claim 3, wherein said second switch means includes two switches each having actuating members, the air valve is a rotary valve with a shaft, positioned in a casing defining the air intake and rotatable on said shaft between a position at which the valve obstructs the intake and a position at which the intake is generally unobstructed, and the operative connection of the second switch means and the air valve includes cam means on the shaft and supporting said actuating members, one of said switches being connected to control the oil supply device and being actuated by the cam means when the air valve is partially open and the other switch being connected to the ignition device and being actuated by the cam means when the air valve is fully open.

5. In a burner as set forth in claim 4, wherein the air valve operating device includes a spring normally urging said device to the valve closed position and an electric servomotor for opening the valve when the servomotor is energized, and the circuit means connects the first switch means to the air valve operating device to energize said servomotor after the temperature in the burner has reached a given temperature.

6. In a burner as set forth in claim 5, wherein said given temperature is less than said predetermined temperature.

7. In a burner as set forth in claim 1, wherein the air valve operating device includes a spring normally urging said device to the valve closed position and an electric servomotor for opening the valve when the servomotor is energized, and the circuit means connects the first switch means to the air valve operating device to energize said servomotor after the temperature in the burner has reached a given temperature.

8. In a burner as set forth in claim 7, wherein said first switch means deenergizes said heater when the temperature in the burner has been raised to a predetermined temperature.

9. In a burner as set forth in claim 8, wherein said sec- 0nd switch means includes a switch having an actuating member, the air valve is a rotary valve with a shaft, positioned in a casing defining the air intake and rotatable on said shaft between a position at which the valve obstructs the intake and a position at which the intake is generally unobstructed, and the operative connection of the second switch means and the air valve includes cam means on the shaft and supporting said actuating member, said switch being connected to control the oil supply de- References Cited UNITED STATES PATENTS Shepperd et al.

vice and being actuated by the cam means when the air 10 JAMES W. WESTHAVER, Primary Examiner.

valve is partially open. 

